b

1

No one wants to be alone

2

Chemical bonding

CHEMICAL BONDING

.Types of bonds

.Octect rule

.Valence bond theory

.VSEPR theory

3

--

--

--

-

Na- -

--

-

-

4

The Rule – Ionic Compounds

5

08-Dec-13 6

Sodium has 1 valence electron

Cl: 1s22s22p63s23p5Na: 1s22s22p63s1

Chlorine has 7 valence electrons An electron transferred gives

each an octet

Cl17

---

--

--

-

--

--

--

--

-

Na- -

--

-- -

--

-

-

Na+ 1s22s22p6

This transfer forms ions, each with an octet forms

Cl- 1s22s22p63s23p6

The resulting ions come together due to electrostatic attraction forming Nacl

7

Properties of Ionic Compounds

Structure: Crystalline solids

Melting point: Generally high

Boiling Point: Generally high

Electrical Conductivity:

Excellent conductors, molten and aqueous

Solubility in water:

Generally soluble

8

Covalent BondingThe bond arises from the mutual attraction of 2 nuclei

for the same electrons.

9

HB+ H

AH

BH

A

A covalent bond is a balance

of attractive and repulsive forces.

A covalent bond is formed by the overlap of orbital's of one atom ,with the orbital of another atom

1. Only an orbital with unpaired electrons is eligible for overlapping

2. For orbital to overlap, the electrons in overlapping orbital's should spin in the opposite direction

3. After overlapping the shape of orbital's change suchthat a greater electron density Appear between the nuclei of atoms along internuclear axis

Conditions for overlapping are :

10

The factor which decides the strength of covalent bond is the extent of overlap, it

depends on the shape of orbital's .The spherical ‘s’orbital’s can not overlap

efficiently, where as the extent of overlapping the dumb bell shaped

p orbital's more

11

Strength of covalent bond

Overlapping Of Orbital'ss-s overlapIt involves mutual overlap of half filled s-orbitals of the atoms

approaching to form a bond. s-p overlapIt involves mutual overlap of half filled s-orbitals of the one

atom with half filled p-orbital of the other..p-p overlapIt involves mutual overlap of half filled p-orbitals of the two

atoms.

Order of strength of overlapping : p-p > s-p > s-s 12

Sigma bond (σ)Sigma bond is formed by an axial or head-on overlapping of pure atomic orbital's It

is end to end overlap. Sigma bonds are re presented by Greek latter σExamples: (σ bond)

13

Pi bond (∏) A pi body is formed by the sidewise overlapping of pure atomic

orbital's.the extent of overlapping is less, hence a pi bond is weaker than σ bond

A bond pair means 2 electrons involved in bonding

Alone pair means a pair of 2 electrons not involved in bonding

14

••

H Cl••

••

This is a LEWIS ELECTRON DOT structure.

shared or bond pair

Unshared or

lone pair (LP)

VSEPR THEORY and MOLECULAR GEOMETRY

This theory helps in explaining the shapes of single covalentmolecules. according to this theory the Various electron pairsaround a central atom orient themselves in a such way that thereis minimum repulsion and maximumstabilityThe decreasing order of repulsions among electron pairs is asunder

Lone pair -Lone pair > Lone pair-Bond pair > Bond pair -Bond pair

15

(Valence Shell Electron Pair Repulsion)

Steric Number 1

17

StericNo.

Basic Geometry

0 lone pair 1 lone pair2 lone pairs 3 lone pairs 4 lone pairs

1linear

1 atom bonded to another atom

Steric Number 2

18

StericNo.

Basic Geometry

0 lone pair1 lone pair 2 lone pairs 3 lone pairs

2linear linear

2 atoms, or lone electron pairs, or a combination of the two, bonded to a central atom.

Steric Number 3

08-Dec-13 19

StericNo.

Basic Geometry

0 lone pair1 lone pair 2 lone pairs 3 lone pairs

3trigonal planar bent / angular linear

3 atoms, or lone electron pairs, or a combination of the two, bonded to a central atom.

Steric Number 4

20

StericNo.

Basic Geometry

0 lone pair1 lone pair

2 lone pairs 3 lone pairs

4tetrahedral

trigonalpyramid bent / angular linear

4 atoms, or lone electron pairs, or a combination of the two, bonded to a central atom.

Steric Number 5

21

StericNo.

Basic Geometry

0 lone pair 1 lone pair 2 lone pairs 3 lone pairs

5trigonal

bipyramidsawhorse /

seesaw t-shape linear

5 atoms, or lone electron pairs, or a combination of the two, bonded to a central atom.

Steric Number 6

22

StericNo.

Basic Geometry

0 lone pair 1 lone pair 2 lone pairs 3 lone pairs

6Octahedral square pyramid square planar

6 atoms, or lone electron pairs, or a combination of the two, bonded to a central atom.

Steric Number 7

23

StericNo.

Basic Geometry

0 lone pair 1 lone pair 2 lone pairs 3 lone pairs

7pentagonal bipyramidal

pentagonal pyramidal

7 atoms, or lone electron pairs, or a combination of the two, bonded to a central atom.

24